Polymerization process using metallocene catalyst systems

ABSTRACT

The present invention relates to a polymerization process using improved metallocene catalyst systems. Specifically, the catalyst systems of the present invention relate to a metallocene compound having optimized metals loading and activator concentration, and demonstrate improved operability and productivity. In an exemplary embodiment, the improved metallocene catalyst system of the present invention comprises a metallocene catalyst compound activated by methylaluminoxane, and a support material, the methylaluminoxane being present in the range of from 3 to 9 mmole methylaluminoxane per gram of support material, and the metallocene being present in the range of from 0.01 to 1.0 mmole metallocene per gram of support material.

FIELD OF THE INVENTION

The present invention relates to a polymerization process using improvedmetallocene catalyst systems. Specifically, the catalyst systems of thepresent invention relate to a metallocene catalyst compound havingoptimized metals loading and activator concentration, and demonstrateimproved operability and productivity.

BACKGROUND OF THE INVENTION

Advances in polymerization and catalysis have resulted in the ability toproduce many new polymers having improved physical and chemicalproperties useful in a wide variety of superior products andapplications. With the development of new catalysts, the choice ofpolymerization (solution, slurry, high pressure or gas phase) forproducing a particular polymer have been greatly expanded. Also,advances in polymerization technology have provided more efficient,highly productive and economically enhanced processes. Especiallyillustrative of these advances is the development of the technologyfield utilizing metallocene catalyst systems.

As with any new technology field, particularly in the polyolefinsindustry, a small savings in cost often determines whether a commercialendeavor is even feasible. This aspect of the metallocene technologyfield is evident by the number of participants in the industry lookingfor new ways to reduce cost. In particular, there has been tremendousfocus in the industry on developing new and improved metallocenecatalyst systems. Some have focused on designing the catalyst systems toproduce new polymers, others on improved operability, and many more onimproving catalyst productivity. The productivity of a catalyst, thatis, the amount of polymer produced per gram of the catalyst, usually isthe key economic factor that can make or break a new commercialdevelopment in the polyolefin industry. Reactor operability—lack offouling and sheeting, etc., of the polymerization reactor—is also amajor concern for polyolefin producers. Reducing the occurrence ofreactor fouling has commercial benefits in reduced down time for thereactor and improved output of polyolefin resin, as well as higherquality resin.

From the early stages in the metallocene technology field, beginningwith the discovery of the utility of alumoxane as a cocatalyst in theearly 1980's, to the discovery of substitutions on the bulky ligands ofthe metallocene compounds, through the development of non-coordinatinganions, and today with the ever-increasing number of new metallocenebulky ligand compounds, catalyst productivity has been a primary focus.

Considering the discussion above, there is still a need for higherproductivity catalyst systems capable of providing the efficienciesnecessary for implementing commerical polyolefin processes. Further, ithas been found, especially in gas phase fluidized bed processes, thatreactor performance (presence or absence of reactor fouling, sheeting,etc.) is an issue when using supported metallocene catalysts. Secondaryadditives or support “surface modifiers” are often used to reducefouling and hence improve commercial performance of the reactor.Addition of these surface modifiers, however, adds cost and complexityto the polymerization process. Thus, it would be highly advantageous tohave a polymerization process and catalyst system capable of producingpolyolefins with improved catalyst productivities and reactorperformance.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present disclosure and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is a plot illustrating the relationship between the metallocene(MCN) concentration and the methylaluminoxane (MAO) concentration of anexemplary embodiment of a catalyst composition of the present invention,with the corresponding activity demonstrated when the exemplary catalystcomposition was utilized in an exemplary embodiment of a polymerizationprocess of the present invention.

FIG. 2 is a plot illustrating the relationship between the metallocene(MCN) concentration and the methylaluminoxane (MAO) concentration of anexemplary embodiment of a catalyst composition of the present invention,with the corresponding bulk density of the polymer produced when theexemplary catalyst composition was utilized in an exemplary embodimentof a polymerization process of the present invention.

While the present invention is susceptible to various modifications andalternative forms, specific exemplary embodiments thereof have beenshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

SUMMARY OF THE INVENTION

The present invention relates to a polymerization process using improvedmetallocene catalyst systems. The catalyst systems of the presentinvention relate to a metallocene catalyst compound having optimizedmetals loading and activator concentration, and demonstrate improvedoperability and productivity.

In one embodiment, the present invention provides a process ofpolymerizing olefins by contacting, in a reactor: (a) ethylene and atleast one comonomer selected from the group consisting of C4 to C8 alphaolefins; and (b) a supported catalyst system comprising a metallocenecatalyst compound activated by methylaluminoxane, and a supportmaterial, the methylaluminoxane being present in the range of from 3 to9 mmole methylaluminoxane per gram of support material, the metallocenebeing present in the range of from 0.01 to 1.0 mmole metallocene pergram of support material. In this embodiment, the catalyst has anactivity of at least 2,500 grams polyethylene per gram of catalystcompound per hour, and the process produces a polymer having a bulkdensity of at least 0.30 gram/cubic centimeter.

In another embodiment, the present invention provides a supportedcatalyst system with a metallocene catalyst compound activated bymethylaluminoxane, and a support material. The methylaluminoxane ispresent in the range of from 3 to 9 mmole methylaluminoxane per gram ofsupport material, and the metallocene is present in the range of from0.01 to 1.0 mmole metallocene per gram of support material.

DETAILED DESCRIPTION OF THE INVENTION

Introduction

The present invention is generally directed toward a process forpolymerizing olefins in the presence of a metallocene catalyst compoundhaving an optimized metals loading and activator concentration, and incertain exemplary embodiments, a process for polymerizing ethylene andC₃ to C₂₀ olefins using a supported metallocene activated bymethylaluminoxane (MAO).

In certain circumstances, as the ratio of metallocene to supportmaterial (the “metallocene loading”) is increased for a constant ratioof MAO to support material (“MAO loading”), the activity of the catalystincreases without a corresponding undesirable increase in fouling, andthe bulk density of the product resin may be constant or marginallyreduced. Generally, as the metallocene loading is held constant, anincrease in the MAO loading increases the catalyst activity, as well asthe bulk density of the product resin, while maintaining the foulingcharacteristics of the catalyst within acceptable tolerances.

General Definitions

As used herein, in reference to Periodic Table “Groups” of Elements, the“new” numbering scheme for the Periodic Table Groups is used, as in theCRC HANDBOOK OF CHEMISTRY AND PHYSICS (David R. Lide ed., CRC Press81^(st) ed. 2000).

As used herein, the phrase “leaving group” refers to one or morechemical moieties bound to the metal center of the catalyst component,which can be abstracted from the catalyst component by an activator,thus producing a species active towards olefin polymerization oroligomerization. The activator is described further below.

As used herein, the term “substituted” means that the group followingthat term possesses at least one moiety in place of one or morehydrogens in any position, which moieties are selected from such groupsas halogen radicals (e.g., Cl, F, Br), hydroxyl groups, carbonyl groups,carboxyl groups, amine groups, phosphine groups, alkoxy groups, phenylgroups, naphthyl groups, C₁ to C₁₀ alkyl groups, C₂ to C₁₀ alkenylgroups, and combinations thereof. Examples of substituted alkyls andaryls include, but are not limited to, acyl radicals, alkylaminoradicals, alkoxy radicals, aryloxy radicals, alkylthio radicals,dialkylamino radicals, alkoxycarbonyl radicals, aryloxycarbonylradicals, carbomoyl radicals, alkyl- and dialkyl-carbamoyl radicals,acyloxy radicals, acylamino radicals, arylamino radicals, andcombinations thereof.

As used herein, structural formulas are employed in manners that arecommonly understood in the chemical arts. For example, the lines (“—”)that are used to represent associations between a metal atom (“M”, Group3 to Group 12 atoms) and a ligand or ligand atom (e.g.,cyclopentadienyl, nitrogen, oxygen, halogen ions, alkyl, etc.), as wellas the phrases “associated with”, “bonded to” and “bonding”, are notlimited to representing a certain type of chemical bond, as these linesand phrases are meant to represent a “chemical bond” in general. As usedherein, the phrase “chemical bond” is defined as an attractive forcebetween atoms that is strong enough to permit the combined aggregate tofunction as a unit, or “compound”.

A certain stereochemistry for a given structure or part of a structureshould not be implied unless so stated for a given structure or apparentby use of commonly used bonding symbols, such as by dashed lines and/orheavy lines.

Unless stated otherwise, no embodiment of the present invention isherein limited to the oxidation state of the metal atom “M” as definedbelow in the individual descriptions and examples that follow. Theligation of the metal atom “M” is such that the compounds describedherein are neutral, unless otherwise indicated.

The “Fouling Index” illustrates the operability of the catalyst. Thehigher the Fouling Index, the greater the fouling observed. A FoulingIndex of zero indicates substantially no fouling, or no visible fouling.A Fouling Index of 1 indicates light fouling, for example, where a verylight partial coating of polymer on the stirrer blades of a 2 literslurry isobutane polymerization reactor, and/or no reactor bodysheeting, are observed. A Fouling Index of 2 indicates more than lightfouling, for example, where the stirrer blades have a heavier,painted-like, coating of polymer and/or the reactor body wall has somesheeting in a band of 1 to 2 inches (2.54 to 5.08 cm) wide on thereactor wall. A Fouling Index of 3 is considered medium fouling, forexample, where the stirrer blade has a thicker, latex/like, coating ofpolymer on the stirrer blade, some soft chunks in the reactor, and/orsome reactor body sheeting within a ban of 2 to 3 inches (5.08 to 7.62cm) wide on the reactor wall. A Fouling Index of 4, for example,evidences more than medium fouling, where the stirrer has a thick,latex-like coating, some harder chunks/balls of polymer, and/or thereactor body wall sheeting band is from 3 to 4 inches (7.62 to 10.2 cm)wide.

Metallocene Catalyst Compounds

The catalyst system useful in the present invention includes at leastone metallocene catalyst component as described herein. Metallocenecatalyst compounds are generally described throughout in, for example, 1& 2 METALLOCENE-BASED POLYOLEFINS (John Scheirs & W. Kaminsky eds., JohnWiley & Sons, Ltd. 2000); G. G. Hlatky in 181 COORDINATION CHEM. REV.243–296 (1999) and in particular, for use in the synthesis ofpolyethylene in 1 METALLOCENE-BASED POLYOLEFINS 261–377 (2000). Themetallocene catalyst compounds as described herein include “halfsandwich” and “full sandwich” compounds having one or more Cp ligands(cyclopentadienyl and ligands isolobal to cyclopentadienyl) bound to atleast one Group 3 to Group 12 metal atom, and one or more leavinggroup(s) bound to the at least one metal atom. Hereinafter, thesecompounds will be referred to as “metallocenes” or “metallocene catalystcomponents”. The metallocene catalyst component is supported on asupport material, in a particular exemplary embodiment as describedfurther below, and may be supported with, or without, another catalystcomponent.

The Cp ligands are one or more rings or ring system(s), at least aportion of which includes π-bonded systems, such as cycloalkadienylligands and heterocyclic analogues. The ring(s) or ring system(s)typically comprise atoms selected from the group consisting of Groups 13to 16 atoms, and, in a particular exemplary embodiment, the atoms thatmake up the Cp ligands are selected from the group consisting of carbon,nitrogen, oxygen, silicon, sulfur, phosphorous, germanium, boron andaluminum and combinations thereof, wherein carbon makes up at least 50%of the ring members. In a more particular exemplary embodiment, the Cpligand(s) are selected from the group consisting of substituted andunsubstituted cyclopentadienyl ligands and ligands isolobal tocyclopentadienyl, non-limiting examples of which includecyclopentadienyl, indenyl, fluorenyl and other structures. Furthernon-limiting examples of such ligands include cyclopentadienyl,cyclopentaphenanthreneyl, indenyl, benzindenyl, fluorenyl,octahydrofluorenyl, cyclooctatetraenyl, cyclopentacyclododecene,phenanthrindenyl, 3,4-benzofluorenyl, 9-phenylfluorenyl,8-H-cyclopent[a]acenaphthylenyl, 7H-dibenzofluorenyl,indeno[1,2-9]anthrene, thiophenoindenyl, thiophenofluorenyl,hydrogenated versions thereof (e.g., 4,5,6,7-tetrahydroindenyl, or“H₄Ind”), substituted versions thereof (as described in more detailbelow), and heterocyclic versions thereof.

The metal atom “M” of the metallocene catalyst compound, as describedthroughout the specification and claims, may be selected from the groupconsisting of Groups 3 through 12 atoms and lanthanide Group atoms inone exemplary embodiment; and selected from the group consisting ofGroups 3 through 10 atoms in a more particular exemplary embodiment, andselected from the group consisting of Sc, Ti, Zr, Hf, V, Nb, Ta, Mn, Re,Fe, Ru, Os, Co, Rh, Ir, and Ni in yet a more particular exemplaryembodiment; and selected from the group consisting of Groups 4, 5 and 6atoms in yet a more particular exemplary embodiment, and Ti, Zr, Hfatoms in yet a more particular exemplary embodiment, and Zr in yet amore particular exemplary embodiment. The oxidation state of the metalatom “M” may range from 0 to +7 in one exemplary embodiment; and in amore particular exemplary embodiment, may be +1, +2, +3, +4 or +5; andin yet a more particular exemplary embodiment may be +2, +3 or +4. Thegroups bound to the metal atom “M” are such that the compounds describedbelow in the formulas and structures are electrically neutral, unlessotherwise indicated. The Cp ligand(s) form at least one chemical bondwith the metal atom M to form the “metallocene catalyst compound”. TheCp ligands are distinct from the leaving groups bound to the catalystcompound in that they are not highly susceptible tosubstitution/abstraction reactions.

In one aspect of the invention, the one or more metallocene catalystcomponents of the invention are represented by the formula (I):Cp^(A)Cp^(B)MX_(n)  (I)wherein M is as described above;

-   -   each X is chemically bonded to M;    -   each Cp group is chemically bonded to M; and    -   n is 0 or an integer from 1 to 4, and either 1 or 2 in a        particular exemplary embodiment.

The ligands represented by Cp^(A) and Cp^(B) in formula (I) may be thesame or different cyclopentadienyl ligands or ligands isolobal tocyclopentadienyl, either or both of which may contain heteroatoms andeither or both of which may be substituted by a group R. In oneexemplary embodiment, Cp^(A) and Cp^(B) are independently selected fromthe group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl,fluorenyl, and substituted derivatives of each.

Independently, each Cp^(A) and Cp^(B) of formula (I) may beunsubstituted or substituted with any one or combination of substituentgroups R. Non-limiting examples of substituent groups R as used instructure (I) as well as ring substituents in structures (Va–d) includegroups selected from the group consisting of hydrogen radicals, alkyls,alkenyls, alkynyls, cycloalkyls, aryls, acyls, aroyls, alkoxys,aryloxys, alkylthiols, dialkylamines, alkylamidos, alkoxycarbonyls,aryloxycarbonyls, carbomoyls, alkyl- and dialkyl-carbamoyls, acyloxys,acylaminos, aroylaminos, and combinations thereof. More particularnon-limiting examples of alkyl substituents R associated with formulas(I) through (Va–d) include methyl, ethyl, propyl, butyl, pentyl, hexyl,cyclopentyl, cyclohexyl, benzyl, phenyl, methylphenyl, andtert-butylphenyl groups and the like, including all their isomers, forexample, tertiary-butyl, isopropyl, and the like. Other possibleradicals include substituted alkyls and aryls such as, for example,fluoromethyl, fluroethyl, difluroethyl, iodopropyl, bromohexyl,chlorobenzyl and hydrocarbyl substituted organometalloid radicalsincluding trimethylsilyl, trimethylgermyl, methyldiethylsilyl and thelike; and halocarbyl-substituted organometalloid radicals, includingtris(trifluoromethyl)silyl, methylbis(difluoromethyl)silyl,bromomethyldimethylgermyl and the like; and disubstituted boron radicalsincluding dimethylboron, for example; and disubstituted Group 15radicals including dimethylamine, dimethylphosphine, diphenylamine,methylphenylphosphine, as well as Group 16 radicals including methoxy,ethoxy, propoxy, phenoxy, methylsulfide and ethylsulfide. Othersubstituents R include, but are not limited to, olefins such asolefinically unsaturated substituents including vinyl-terminated ligandssuch as, for example, 3-butenyl, 2-propenyl, 5-hexenyl and the like. Inone exemplary embodiment, at least two R groups (two adjacent R groupsin a particular exemplary embodiment) are joined to form a ringstructure having from 3 to 30 atoms selected from the group consistingof carbon, nitrogen, oxygen, phosphorous, silicon, germanium, aluminum,boron and combinations thereof. Also, a substituent group R group suchas 1-butanyl may form a bonding association to the element M.

Each X in the formula (I) above and for the formulae/structures (II)through (Va–d) below is independently selected from the group consistingof: any leaving group, in one exemplary embodiment; halogen ions,hydrides, C₁ to C₁₂ alkyls, C₂ to C₁₂ alkenyls, C₆ to C₁₂ aryls, C₇ toC₂₀ alkylaryls, C₁ to C₁₂ alkoxys, C₆ to C₁₆ aryloxys, C₇ to C₁₈alkylaryloxys, C₁ to C₁₂ fluoroalkyls, C₆ to C₁₂ fluoroaryls, and C₁ toC₁₂ heteroatom-containing hydrocarbons and substituted derivativesthereof in a more particular exemplary embodiment; hydride, halogenions, C₁ to C₆ alkyls, C₂ to C₆ alkenyls, C₇ to C₁₈ alkylaryls, C₁ to C₆alkoxys, C₆ to C₁₄ aryloxys, C₇ to C₁₆ alkylaryloxys, C₁ to C₆alkylcarboxylates, C₁ to C₆ fluorinated alkylcarboxylates, C₆ to C₁₂arylcarboxylates, C₇ to C₁₈ alkylarylcarboxylates, C₁ to C₆fluoroalkyls, C₂ to C₆ fluoroalkenyls, and C₇ to C₁₈ fluoroalkylaryls inyet a more particular exemplary embodiment; hydride, chloride, fluoride,methyl, phenyl, phenoxy, benzoxy, tosyl, fluoromethyls and fluorophenylsin yet a more particular exemplary embodiment; C₁ to C₁₂ alkyls, C₂ toC₁₂ alkenyls, C₆ to C₁₂ aryls, C₇ to C₂₀ alkylaryls, substituted C₁ toC₁₂ alkyls, substituted C₆ to C₁₂ aryls, substituted C₇ to C₂₀alkylaryls and C₁ to C₁₂ heteroatom-containing alkyls, C₁ to C₁₂heteroatom-containing aryls and C₁ to C₁₂ heteroatom-containingalkylaryls in yet a more particular exemplary embodiment; chloride,fluoride, C₁ to C₆ alkyls, C₂ to C₆ alkenyls, C₇ to C₁₈ alkylaryls,halogenated C₁ to C₆ alkyls, halogenated C₂ to C₆ alkenyls, andhalogenated C₇ to C₁₈ alkylaryls in yet a more particular exemplaryembodiment; fluoride, methyl, ethyl, propyl, phenyl, methylphenyl,dimethylphenyl, trimethylphenyl, fluoromethyls (mono-, di- andtrifluoromethyls) and fluorophenyls (mono-, di-, tri-, tetra- andpentafluorophenyls) in yet a more particular exemplary embodiment; andfluoride in yet a more particular exemplary embodiment.

Other non-limiting examples of X groups include amines, phosphines,ethers, carboxylates, dienes, hydrocarbon radicals having from 1 to 20carbon atoms, fluorinated hydrocarbon radicals (e.g., —C₆F₅(pentafluorophenyl)), fluorinated alkylcarboxylates (e.g., CF₃C(O)O⁻),hydrides, halogen ions and combinations thereof. Other examples of Xligands include alkyl groups such as cyclobutyl, cyclohexyl, methyl,heptyl, tolyl, trifluoromethyl, tetramethylene, pentamethylene,methylidene, methyoxy, ethyoxy, propoxy, phenoxy, bis(N-methylanilide),dimethylamide, dimethylphosphide radicals and the like. In one exemplaryembodiment, two or more X's form a part of a fused ring or ring system.

In another aspect of the invention, the metallocene catalyst componentincludes those of formula (I) where Cp^(A) and Cp^(B) are bridged toeach other by at least one bridging group, (A), such that the structureis represented by formula (II):Cp^(A)(A)Cp^(B)Mx_(n)  (II)These bridged compounds represented by formula (II) are known as“bridged metallocenes”. The elements Cp^(A), Cp^(B), M, X and n instructure (II) are as defined above for formula (I); wherein each Cpligand is chemically bonded to M, and (A) is chemically bonded to eachCp. Non-limiting examples of bridging group (A) include divalenthydrocarbon groups containing at least one Group 13 to 16 atom, such as,but not limited to, at least one of a carbon, oxygen, nitrogen, silicon,aluminum, boron, germanium and tin atom and combinations thereof;wherein the heteroatom may also be C₁ to C₁₂ alkyl or aryl substitutedto satisfy neutral valency. The bridging group (A) may also containsubstituent groups R as defined above (for formula (I)) includinghalogen radicals and iron. More particular non-limiting examples ofbridging group (A) are represented by C₁ to C₆ alkylenes, substituted C₁to C₆ alkylenes, oxygen, sulfur, R′₂C═, R′₂Si═, ═Si(R′)₂Si(R′₂)═,R′₂Ge═, and R′P═ (wherein “═” represents two chemical bonds), where R′is independently selected from the group consisting of hydride,hydrocarbyl, substituted hydrocarbyl, halocarbyl, substitutedhalocarbyl, hydrocarbyl-substituted organometalloid,halocarbyl-substituted organometalloid, disubstituted boron,disubstituted Group 15 atoms, substituted Group 16 atoms, and halogenradical; and wherein two or more R′ may be joined to form a ring or ringsystem. In one exemplary embodiment, the bridged metallocene catalystcomponent of formula (II) has two or more bridging groups (A).

Other non-limiting examples of bridging group (A) include methylene,ethylene, ethylidene, propylidene, isopropylidene, diphenylmethylene,1,2-dimethylethylene, 1,2-diphenylethylene, 1,1,2,2-tetramethylethylene,dimethylsilyl, diethylsilyl, methyl-ethylsilyl,trifluoromethylbutylsilyl, bis(trifluoromethyl)silyl, di(n-butyl)silyl,di(n-propyl)silyl, di(i-propyl)silyl, di(n-hexyl)silyl,dicyclohexylsilyl, diphenylsilyl, cyclohexylphenylsilyl,t-butylcyclohexylsilyl, di(t-butylphenyl)silyl, di(p-tolyl)silyl and thecorresponding moieties wherein the Si atom is replaced by a Ge or a Catom; as well as dimethylsilyl, diethylsilyl, dimethylgermyl anddiethylgermyl.

In another exemplary embodiment, bridging group (A) may also be cyclic,having, for example, 4 to 10 ring members; in a more particularexemplary embodiment, bridging group (A) may have 5 to 7 ring members.The ring members may be selected from the elements mentioned above, and,in a particular exemplary embodiment, are selected from one or more ofB, C, Si, Ge, N and O. Non-limiting examples of ring structures whichmay be present as, or as part of, the bridging moiety arecyclobutylidene, cyclopentylidene, cyclohexylidene, cycloheptylidene,cyclooctylidene and the corresponding rings where one or two carbonatoms are replaced by at least one of Si, Ge, N and O. In a moreparticular exemplary embodiment, one or two carbon atoms are replaced byat least one of Si and Ge. The bonding arrangement between the ring andthe Cp groups may be either cis-, trans-, or a combination.

The cyclic bridging groups (A) may be saturated or unsaturated and/ormay carry one or more substituents and/or may be fused to one or moreother ring structures. If present, the one or more substituents are, inone exemplary embodiment, selected from the group consisting ofhydrocarbyl (e.g., alkyl, such as methyl) and halogen (e.g., F, Cl). Theone or more Cp groups to which the above cyclic bridging moieties mayoptionally be fused may be saturated or unsaturated, and are selectedfrom the group consisting of those having 4 to 10, more particularly 5,6 or 7 ring members (selected from the group consisting of C, N, O and Sin a particular exemplary embodiment) such as, for example, cyclopentyl,cyclohexyl and phenyl. Moreover, these ring structures may themselves befused such as, for example, in the case of a naphthyl group. Moreover,these (optionally fused) ring structures may carry one or moresubstituents. Illustrative, non-limiting examples of these substituentsare hydrocarbyl (particularly alkyl) groups and halogen atoms.

The ligands Cp^(A) and Cp^(B) of formulae (I) and (II) are differentfrom each other in one exemplary embodiment, and the same in anotherexemplary embodiment.

In yet another aspect of the invention, the metallocene catalystcomponents include bridged mono-ligand metallocene compounds (e.g., monocyclopentadienyl catalyst components). In this embodiment, the at leastone metallocene catalyst component is a bridged “half-sandwich”metallocene represented by the formula (III):Cp^(A)(A)QMX_(r)  (III)wherein Cp^(A) is defined above and is bound to M;

-   -   (A) is a bridging group bonded to Q and Cp^(A); and    -   an atom from the Q group is bonded to M; and r is an integer 0,        1 or 2.

In formula (III) above, Cp^(A), (A) and Q may form a fused ring system.The X groups of formula (II) are as defined above in formula (I) and(II). In one exemplary embodiment, Cp^(A) is selected from the groupconsisting of cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl,substituted versions thereof, and combinations thereof.

In formula (II), Q is a heteroatom-containing ligand in which thebonding atom (the atom that is bonded with the metal M) is, in oneexemplary embodiment, selected from the group consisting of Group 15atoms and Group 16 atoms. In yet a more particular embodiment, thebonding atom is selected from the group consisting of nitrogen,phosphorus, oxygen or sulfur atoms. In still a more particularembodiment, the bonding atom is selected from the group consisting ofnitrogen and oxygen. Non-limiting examples of Q groups includealkylamines, arylamines, mercapto compounds, ethoxy compounds,carboxylates (e.g., pivalate), carbamates, azenyl, azulene, pentalene,phosphoyl, phosphinimine, pyrrolyl, pyrozolyl, carbazolyl, borabenzeneother compounds havinging Group 15 and Group 16 atoms capable of bondingwith M.

In yet another aspect of the invention, the at least one metallocenecatalyst component is an unbridged “half sandwich” metallocenerepresented by the formula (IVa):Cp^(A)MQ_(q)X_(w)  (IVa)wherein Cp^(A) is defined as for the Cp groups in (I) and is a ligandthat is bonded to M;

-   -   each Q is independently bonded to M;    -   X is a leaving group as described above in (I);    -   w ranges from 0 to 3, and is 0 or 3 in one exemplary embodiment;    -   q ranges from 0 to 3, and is 0 or 3 in one exemplary embodiment.

In one exemplary embodiment, Cp^(A) is selected from the groupconsisting of cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl,substituted version thereof, and combinations thereof. In formula (IVa),Q is selected from the group consisting of ROO⁻, RO—, R(O)—, —NR—,—CR₂—, —S—, —NR₂, —CR₃, —SR, —SiR₃, —PR₂, —H, and substituted andunsubstituted aryl groups, R is selected from the group consisting of C₁to C₆ alkyls, C₆ to C₁₂ aryls, C₁ to C₆ alkylamines, C₆ to C₁₂alkylarylamines, C₁ to C₆ alkoxys, C₆ to C₁₂ aryloxys, and the like.Non-limiting examples of Q include C₁ to C₁₂ carbamates, C₁ to C₁₂carboxylates (e.g., pivalate), C₂ to C₂₀ allyls, and C₂ to C₂₀heteroallyl moieties.

Described another way, the “half sandwich” metallocenes above can bedescribed as in formula (IVb), such as described in, for example, U.S.Pat. No. 6,069,213:Cp^(A)M(W₂GZ)X_(y) orT(Cp^(A)M(W₂GZ)X_(y))_(m)  (IVb)wherein M, Cp^(A), and X are as defined above;

-   -   W₂GZ forms a polydentate ligand unit (e.g., pivalate), wherein        at least one of the W groups form a bond with M, and is defined        such that each W is independently selected from the group        consisting of —O—, —NR—, —CR₂— and —S—; G is either carbon or        silicon; and Z is selected from the group consisting of R, —OR,        —NR₂, —CR₃, —SR, —SiR₃, —PR₂, and hydride, providing that when W        is —NR—, then Z is selected from the group consisting of —OR,        —NR₂, —SR, —SiR₃, —PR₂; and provided that neutral valency for W        is satisfied by Z; and wherein each R is independently selected        from the group consisting of C₁ to C₁₀ heteroatom containing        groups, C₁ to C₁₀ alkyls, C₆ to C₁₂ aryls, C₆ to C₁₂ alkylaryls,        C₁ to C₁₀ alkoxys, and C₆ to C₁₂ aryloxys;    -   y is 1 or 2 in a particular embodiment;    -   T is a bridging group selected from the group consisting of C₁        to C₁₀ alkylenes, C₆ to C₁₂ arylenes and C₁ to C₁₀ heteroatom        containing groups, and C₆ to C₁₂ heterocyclic groups; wherein        each T group bridges adjacent “Cp^(A)M(W₂GZ)X_(y)” groups, and        is chemically bonded to the Cp^(A) groups; and    -   m is an integer from 1 to 7. In an exemplary embodiment, m is an        integer from 2 to 6.

In another aspect of the invention, the metallocene catalyst componentcan be described more particularly in structures (Va), (Vb), (Vc) and(Vd):

-   -   wherein in structures (Va) to (Vd) M is selected from the group        consisting of Group 3 to Group 12 atoms, and selected from the        group consisting of Group 3 to Group 10 atoms in a more        particular embodiment, and selected from the group consisting of        Group 3 to Group 6 atoms in yet a more particular embodiment,        and selected from the group consisting of Group 4 atoms in yet a        more particular embodiment, and selected from the group        consisting of Zr and Hf in yet a more particular embodiment; and        is Zr in yet a more particular embodiment;    -   wherein Q in (Va–i) and (Va–ii) is selected from the group        consisting of halogen ions, alkyls, alkylenes, aryls, arylenes,        alkoxys, aryloxys, amines, alkylamines, phosphines,        alkylphosphines, substituted alkyls, substituted aryls,        substituted alkoxys, substituted aryloxys, substituted amines,        substituted alkylamines, substituted phosphines, substituted        alkylphosphines, carbamates, heteroallyls, carboxylates        (non-limiting examples of suitable carbamates and carboxylates        include trimethylacetate, trimethylacetate, methylacetate,        p-toluate, benzoate, diethylcarbamate, and dimethylcarbamate),        fluorinated alkyls, fluorinated aryls, and fluorinated        alkylcarboxylates;    -   q is an integer ranging from 1 to 3;    -   wherein each R* is independently: selected from the group        consisting of hydrocarbyls and heteroatom-containing        hydrocarbyls in one exemplary embodiment; and selected from the        group consisting of alkylenes, substituted alkylenes and        heteroatom-containing hydrocarbyls in another exemplary        embodiment; and selected from the group consisting of C₁ to C₁₂        alkylenes, C₁ to C₁₂ substituted alkylenes, and C₁ to C₁₂        heteroatom-containing hydrocarbons in a more particular        embodiment; and selected from the group consisting of C₁ to C₄        alkylenes in yet a more particular embodiment; and wherein both        R* groups are identical in another exemplary embodiment in        structures (Vb–d);    -   A is as described above for (A) in structure (II), and more        particularly, selected from the group consisting of —O—, —S—,        —SO₂—, —NR—, ═SiR₂, ═GeR₂, ═SnR₂, —R₂SiSiR₂—, RP═, C₁ to C₁₂        alkylenes, substituted C₁ to C₁₂ alkylenes, divalent C₄ to C₁₂        cyclic hydrocarbons and substituted and unsubstituted aryl        groups in one exemplary embodiment; and selected from the group        consisting of C₅ to C₈ cyclic hydrocarbons, —CH₂CH₂—, ═CR₂ and        ═SiR₂ in a more particular embodiment; wherein R is selected        from the group consisting of alkyls, cycloalkyls, aryls,        alkoxys, fluoroalkyls and heteroatom-containing hydrocarbons in        one exemplary embodiment; and R is selected from the group        consisting of C₁ to C₆ alkyls, substituted phenyls, phenyl, and        C₁ to C₆ alkoxys in a more particular embodiment; and R is        selected from the group consisting of methoxy, methyl, phenoxy,        and phenyl in yet a more particular embodiment;    -   wherein A may be absent in yet another exemplary embodiment, in        which case each R* is defined as for R¹-R¹²;    -   each X is as described above in (I);    -   n is an integer from 0 to 4, and from 1 to 3 in another        exemplary embodiment, and 1 or 2 in yet another exemplary        embodiment; and    -   R¹ through R¹² are independently: selected from the group        consisting of hydrogen radical, halogen radicals, C₁ to C₁₂        alkyls, C₂ to C₁₂ alkenyls, C₆ to C₁₂ aryls, C₇ to C₂₀        alkylaryls, C₁ to C₁₂ alkoxys, C₁ to C₁₂ fluoroalkyls, C₆ to C₁₂        fluoroaryls, and C₁ to C₁₂ heteroatom-containing hydrocarbons        and substituted derivatives thereof, in one exemplary        embodiment; selected from the group consisting of hydrogen        radical, fluorine radical, chlorine radical, bromine radical, C₁        to C₆ alkyls, C₂ to C₆ alkenyls, C₇ to C₁₈ alkylaryls, C₁ to C₆        fluoroalkyls, C₂ to C₆ fluoroalkenyls, C₇ to C₁₈        fluoroalkylaryls in a more particular embodiment; and hydrogen        radical, fluorine radical, chlorine radical, methyl, ethyl,        propyl, isopropyl, butyl, isobutyl, tertiary butyl, hexyl,        phenyl, 2,6-di-methylphenyl, and 4-tertiarybutylphenyl groups in        yet a more particular embodiment; wherein adjacent R groups may        form a ring, either saturated, partially saturated, or        completely saturated.

The structure of the metallocene catalyst component represented by (Va)may take on many forms, such as those disclosed in, for example, U.S.Pat. Nos. 5,026,798, 5,703,187, and 5,747,406, including a dimer oroligomeric structure, such as disclosed in, for example, U.S. Pat. Nos.5,026,798 and 6,069,213.

In a particular embodiment of the metallocene represented in (Vd), R¹and R² form a conjugated 6-membered carbon ring system that may or maynot be substituted.

Non-limiting examples of metallocene catalyst components consistent withthe description herein include:

-   cyclopentadienylzirconium X_(n),-   indenylzirconium X_(n),-   (1-methylindenyl)zirconium X_(n),-   (2-methylindenyl)zirconium X_(n),-   (1-propylindenyl)zirconium X_(n),-   (2-propylindenyl)zirconium X_(n),-   (1-butylindenyl)zirconium X_(n),-   (2-butylindenyl)zirconium X_(n),-   (methylcyclopentadienyl)zirconium X_(n),-   tetrahydroindenylzirconium X_(n),-   (pentamethylcyclopentadienyl)zirconium X_(n),-   cyclopentadienylzirconium X_(n),-   pentamethylcyclopentadienyltitanium X_(n),-   tetramethylcyclopentyltitanium X_(n),-   1,2,4-trimethylcyclopentadienylzirconium X_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(cyclopentadienyl)zirconium    X_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(1,2,3-trimethyl-cyclopentadienyl)zirconium    X_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(1,2-dimethyl-cyclopentadienyl)zirconium    X_(n),-   dimethylsilyl(1,2,3,4-tetramethyl-cyclopentadienyl)(2-methylcyclopentadienyl)zirconium    X_(n),-   dimethylsilyl(cyclopentadienyl)(indenyl)zirconium X_(n),-   dimethylsilyl(2-methylindenyl)(fluorenyl)zirconium X_(n),-   diphenylsilyl(1,2,3,4-tetramethyl-cyclopentadienyl)(3-propylcyclopentadienyl)zirconium    X_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)    (3-t-butylcyclopentadienyl)zirconium X_(n),-   dimethylgermyl(1,2-dimethylcyclopentadienyl)(3-isopropylcyclopentadienyl)zirconium    X_(n),-   dimethylsilyl(1,2,3,4-tetramethyl-cyclopentadienyl)(3-methylcyclopentadienyl)zirconium    X_(n),-   diphenylmethylidene(cyclopentadienyl)(9-fluorenyl)zirconium X_(n),-   diphenylmethylidene(cyclopentadienyl)(indenyl)zirconium X_(n),-   iso-propylidenebis(cyclopentadienyl)zirconium X_(n),-   iso-propylidene(cyclopentadienyl)(9-fluorenyl)zirconium X_(n),-   iso-propylidene(3-methylcyclopentadienyl)(9-fluorenyl)zirconium    X_(n),-   ethylenebis(9-fluorenyl)zirconium X_(n),-   meso-ethylenebis(1-indenyl)zirconium X_(n),-   ethylenebis(1-indenyl)zirconium X_(n),-   ethylenebis(2-methyl-1-indenyl)zirconium X_(n),-   ethylenebis(2-methyl-4,5,6,7-tetrahydro-1-indenyl)zirconium X_(n),-   ethylenebis(2-propyl-4,5,6,7-tetrahydro-1-indenyl)zirconium X_(n),-   ethylenebis(2-isopropyl-4,5,6,7-tetrahydro-1-indenyl)zirconium    X_(n),-   ethylenebis(2-butyl-4,5,6,7-tetrahydro-1-indenyl)zirconium X_(n),-   ethylenebis(2-isobutyl-4,5,6,7-tetrahydro-1-indenyl)zirconium X_(n),-   dimethylsilyl(4,5,6,7-tetrahydro-1-indenyl)zirconium X_(n),-   diphenyl(4,5,6,7-tetrahydro-1-indenyl)zirconium X_(n),-   ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium X_(n),-   dimethylsilylbis(cyclopentadienyl)zirconium X_(n),-   dimethylsilylbis(9-fluorenyl)zirconium X_(n),-   dimethylsilylbis(1-indenyl)zirconium X_(n),-   dimethylsilylbis(2-methylindenyl)zirconium X_(n),-   dimethylsilylbis(2-propylindenyl)zirconium X_(n),-   dimethylsilylbis(2-butylindenyl)zirconium X_(n),-   diphenylsilylbis(2-methylindenyl)zirconium X_(n),-   diphenylsilylbis(2-propylindenyl)zirconium X_(n),-   diphenylsilylbis(2-butylindenyl)zirconium X_(n),-   dimethylgermylbis(2-methylindenyl)zirconium X_(n),-   dimethylsilylbis(tetrahydroindenyl)zirconium X_(n),-   dimethylsilylbis(tetramethylcyclopentadienyl)zirconium X_(n),-   dimethylsilyl(cyclopentadienyl)(9-fluorenyl)zirconium X_(n),-   diphenylsilyl(cyclopentadienyl)(9-fluorenyl)zirconium X_(n),-   diphenylsilylbis(indenyl)zirconium X_(n),-   cyclotrimethylenesilyl(tetramethylcyclopentadienyl)(cyclopentadienyl)zirconium    X_(n),-   cyclotetramethylenesilyl(tetramethylcyclopentadienyl)(cyclopentadienyl)zirconium    X_(n),-   cyclotrimethylenesilyl(tetramethylcyclopentadienyl)(2-methylindenyl)zirconium    X_(n),-   cyclotrimethylenesilyl(tetramethylcyclopentadienyl)(3-methylcyclopentadienyl)zirconium    X_(n),-   cyclotrimethylenesilylbis(2-methylindenyl)zirconium X_(n),-   cyclotrimethylenesilyl(tetramethylcyclopentadienyl)(2,3,5-trimethylcyclopentadienyl)zirconium    X_(n),-   cyclotrimethylenesilylbis(tetramethylcyclopentadienyl)zirconium    X_(n),-   dimethylsilyl(tetramethylcyclopentadieneyl)(N-tert-butylamido)titanium    X_(n),-   bis(cyclopentadienyl)chromium X_(n),-   bis(cyclopentadienyl)zirconium X_(n),-   bis(n-butylcyclopentadienyl)zirconium X_(n),-   bis(n-dodecyclcyclopentadienyl)zirconium X_(n),-   bis(ethylcyclopentadienyl)zirconium X_(n),-   bis(iso-butylcyclopentadienyl)zirconium X_(n),-   bis(iso-propylcyclopentadienyl)zirconium X_(n),-   bis(methylcyclopentadienyl)zirconium X_(n),-   bis(n-oxtylcyclopentadienyl)zirconium X_(n),-   bis(n-pentylcyclopentadienyl)zirconium X_(n),-   bis(n-propylcyclopentadienyl)zirconium X_(n),-   bis(trimethylsilylcyclopentadienyl)zirconium X_(n),-   bis(1,3-bis(trimethylsilyl)cyclopentadienyl)zirconium X_(n),-   bis(1-ethyl-2-methylcyclopentadienyl)zirconium X_(n),-   bis(1-ethyl-3-methylcyclopentadienyl)zirconium X_(n),-   bis(pentamethylcyclopentadienyl)zirconium X_(n),-   bis(pentamethylcyclopentadienyl)zirconium X_(n),-   bis(1-propyl-3-methylcyclopentadienyl)zirconium X_(n),-   bis(1-n-butyl-3-methylcyclopentadienyl)zirconium X_(n),-   bis(1-isobutyl-3-methylcyclopentadienyl)zirconium X_(n),-   bis(1-propyl-3-butylcyclopentadienyl)zirconium X_(n),-   bis(1-n-butyl-3-n-butylcyclopentadienyl)zirconium X_(n),-   bis(1,3-methyl-n-butylcyclopentadienyl)zirconium X_(n),-   bis(4,7-dimethylindenyl)zirconium X_(n),-   bis(indenyl)zirconium X_(n),-   bis(2-methylindenyl)zirconium X_(n),-   cyclopentadienylindenylzirconium X_(n),-   (tetramethyl cyclopentadienyl) (n-propyl cyclopentadienyl)zirconium    X_(n),-   (pentamethyl cyclopentadienyl) (n-propyl cyclopentadienyl)zirconium    X_(n),-   bis(n-propylcyclopentadienyl)hafnium X_(n),-   bis(n-butylcyclopentadienyl)hafnium X_(n),-   bis(n-pentylcyclopentadienyl)hafnium X_(n),-   (n-propyl cyclopentadienyl)(n-butyl cyclopentadienyl)hafnium X_(n),-   bis[(2-trimethylsilylethyl)cyclopentadienyl]hafnium X_(n),-   bis(trimethylsilyl cyclopentadienyl)hafnium X_(n),-   bis(2-n-propylindenyl)hafnium X_(n),-   bis(2-n-butylindenyl)hafnium X_(n),-   dimethylsilylbis(n-propylcyclopentadienyl)hafnium X_(n),-   dimethylsilylbis(n-butylcyclopentadienyl)hafnium X_(n),-   bis(9-n-propylfluorenyl)hafnium X_(n),-   bis(9-n-butylfluorenyl)hafnium X_(n),-   (9-n-propylfluorenyl)(2-n-propylindenyl)hafnium X_(n),-   bis(1-n-propyl-2-methylcyclopentadienyl)hafnium X_(n),-   (n-propylcyclopentadienyl)(1-n-propyl-3-n-butylcyclopentadienyl)hafnium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(cyclopropylamido)titanium    X_(n),-   dimethylsilyl(tetramethyleyclopentadienyl)(cyclobutylamido)titanium    X_(n),-   dimethylsilyl(tetramethyleyclopentadienyl)(cyclopentylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(cyclohexylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(cycloheptylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(cyclooctylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(cyclononylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(cyclodecylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(cycloundecylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(cyclododecylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(sec-butylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(n-octylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(n-decylamido)titanium    X_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(n-octadecylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cyclopropylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cyclobutylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cyclopentylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cyclohexylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cycloheptylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cyclooctylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cyclononylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cyclodecylamido)titanium,    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cycloundecylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(cyclododecylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(sec-butylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(n-octylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(n-decylamido)titanium    X_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(n-octadecylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cyclopropylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cyclobutylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cyclopentylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cyclohexylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cycloheptylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cyclooctylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cyclononylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cyclodecylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cycloundecylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(cyclododecylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(sec-butylamido)titanium    X_(n),-   diphenylsilyl(tetramethyleyclopentadienyl)(n-octylamido)titanium    X_(n),-   diphenylsilyl(tetramethyleyclopentadienyl)(n-decylamido)titanium    X_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(n-octadecylamido)titanium    X_(n), and derivatives thereof,    wherein the value of n is 1, 2 or 3. The phrase “derivatives    thereof” will be understood to mean any substitution or ring    formation as described above for structures (Va–d) in one exemplary    embodiment; and in particular, replacement of the metal “M” (Cr, Zr,    Ti or Hf) with an atom selected from the group consisting of Cr, Zr,    Hf and Ti; and replacement of the “X” group with any of C₁ to C₅    alkyls, C₆ aryls, C₆ to C₁₀ alkylaryls, fluorine, chlorine, or    bromine.

It is contemplated that the metallocene catalysts components describedabove include their structural or optical or enantiomeric isomers(racemic mixture), and, in one exemplary embodiment, may be a pureenantiomer.

As used herein, a single, bridged, asymmetrically substitutedmetallocene catalyst component having a racemic and/or meso isomer doesnot, itself, constitute at least two different bridged, metallocenecatalyst components.

The “metallocene catalyst component” useful in the present invention mayinclude any combination of any “embodiment” described herein.

Activator and Activation Methods for the Metallocene Catalyst Compounds

The activator used with the catalyst compositions of the presentinvention is methylaluminoxane (“MAO”). A suitable source of MAO is a 30wt % MAO solution commercially available from Albemarle Corporation, ofBaton Rouge, La. Generally, MAO is present in the catalyst compositionsof the present invention in an amount in the range of from 3 to 9 mmoleMAO/gram of support material. In certain preferred embodiments, the MAOis present in an amount in the range of from 4 to 7.7 mmole MAO/gram ofsupport material. In certain more preferred embodiments, the MAO ispresent in an amount in the range of from 5 to 6.5 mmole MAO/gram ofsupport material. In certain most preferred embodiments, the MAO ispresent in an amount in the range of from 6 to 6.5 mmole MAO/gram ofsupport material. The MAO activator may be associated with or bound to asupport, either in association with the catalyst component (e.g.,metallocene) or separate from the catalyst component, such as describedby Gregory G. Hlatky, Heterogeneous Single-Site Catalysts for OlefinPolymerization, 100(4) CHEMICAL REVIEWS 1347–1374 (2000).

Generally, an increase in the amount of MAO present in the catalystcompositions of the present invention, with all other variables beingheld constant, tends to increase the activity demonstrated by thecatalyst composition when used in the polymerization processes of thepresent invention, as well as increase the bulk density of the polymerproduct that is produced, and also increase the reactor Fouling Indexthat is observed.

For example, the polymerization processes of the present invention,using catalyst systems having MAO present in an amount in the range offrom 3 to 9 mmole MAO/gram of support material, generally have a reactorFouling Index in the range of from 0 to 2; a catalyst activity of atleast 2,500 gram polymer per gram catalyst per hour; and produce apolymer product having a bulk density of at least 0.30 gram per cubiccentimeter. In certain preferred embodiments wherein the MAO is presentin the catalyst system in the range of from 4 to 7.7 mmole MAO/gram ofsupport material, the activity is increased to at least 2,800 grampolymer per gram catalyst per hour; and polymer product is produced thathas a bulk density of at least 0.35 gram per cubic centimeter. Incertain more preferred embodiments wherein the MAO is present in thecatalyst system in the range of from 5 to 6.5 mmole MAO/gram of supportmaterial, the activity is increased to at least 3,500 gram polymer pergram catalyst per hour; the reactor Fouling Index is reduced to 0; andpolymer product is produced that has a bulk density of at least 0.39gram per cubic centimeter. In certain most preferred embodiments whereinthe MAO is present in the catalyst system in the range of from 6 to 6.5mmole MAO/gram of support material, the activity is increased to atleast 4,000 gram polymer per gram catalyst per hour; the Fouling Indexis 0; and polymer product is produced that has a bulk density of atleast 0.45 gram per cubic centimeter.

Referring now to FIG. 1, depicted therein at 100 is a plot illustratingthe relationship between the metallocene (MCN) concentration and themethylaluminoxane (MAO) concentration of an exemplary embodiment of acatalyst composition of the present invention, with the correspondingactivity demonstrated when the exemplary catalyst composition was usedin an exemplary embodiment of a polymerization process of the presentinvention. At 150 is illustrated an exemplary catalyst compositionhaving a metallocene concentration of 0.076 mmole/gram of supportmaterial, and a MAO concentration of 3.84 mmole/gram of supportmaterial, which, when used in an exemplary embodiment of apolymerization process of the present invention, demonstrated anactivity of 4,400 gram polymer per gram catalyst hour. At 155 isillustrated an exemplary catalyst composition also having a metalloceneconcentration of 0.076 mmole/gram of support material, and having a MAOconcentration of 7.68 mmole/gram of support material, which, when usedin an exemplary embodiment of a polymerization process of the presentinvention, demonstrated an activity of 8,319 gram polymer per gramcatalyst hour. At 160 is illustrated an exemplary catalyst compositionhaving a metallocene concentration of 0.038 mmole/gram of supportmaterial, and having a MAO concentration of 7.68 mmole/gram of supportmaterial, which, when used in an exemplary embodiment of apolymerization process of the present invention, demonstrated anactivity of 5,173 gram polymer per gram catalyst hour. At 165 isillustrated an exemplary catalyst composition having a metalloceneconcentration of 0.038 mmole/gram of support material, and having a MAOconcentration of 3.84 mmole/gram of support material, which, when usedin an exemplary embodiment of a polymerization process of the presentinvention, demonstrated an activity of 2,823 gram polymer per gramcatalyst hour. As the foregoing description of four reference pointsdepicted in FIG. 1 illustrates, exemplary catalyst compositions having,for example, comparatively lower MAO and metallocene concentrationsdemonstrated lower activity when used in exemplary polymerizationprocesses of the present invention than did exemplary catalystcompositions having, for example, comparatively higher MAO andmetallocene concentrations.

The relationship between an exemplary catalyst composition'sconcentration of MAO and metallocene, and the activity that may berealized from the use of such exemplary composition in an exemplarypolymerization process may be further evaluated by examination of theactivity regions (e.g., Region 102, 104, 106, 108, 110, 112, 114, 116,118, 120 and 122) depicted in FIG. 1 and summarized in the table below.

TABLE 1 Activity Range Region (gram polymer/gram catalyst · hour) 122less than 3,003 120  3003 to 3,623 118 3,623 to 4,243 116 4,243 to 4,863114 4,863 to 5,482 112 5,482 to 6,102 110 6,102 to 6,722 108 6,722 to7,342 106 7,342 to 7,962 104 7,962 to 8,582 102 above 8,582

For example, an exemplary catalyst composition (depicted at 155) havinga metallocene concentration of 0.076 mmole/gram of support material, andhaving a MAO concentration of 7.68 mmole/gram of support material,demonstrated an activity of 8,319 gram polymer per gram catalyst·hourwhen used in an exemplary embodiment of a polymerization process of thepresent invention, and is therefore located in activity region 104 ofFIG. 1. Similarly, an exemplary catalyst composition (depicted at 165)having a metallocene concentration of 0.038 mmole/gram of supportmaterial, and having a MAO concentration of 3.84 mmole/gram of supportmaterial, demonstrated an activity of 2,823 gram polymer per gramcatalyst·hour when used in an exemplary embodiment of a polymerizationprocess of the present invention, and is therefore located in activityregion 122 of FIG. 1.

Referring now to FIG. 2, depicted therein at 200 is a plot illustratingthe relationship between the metallocene (MCN) concentration and themethylaluminoxane (MAO) concentration of an exemplary embodiment of acatalyst composition of the present invention, with the correspondingbulk density of the polymer produced when the exemplary catalystcomposition was utilized in an exemplary embodiment of a polymerizationprocess of the present invention. At 250 is illustrated an exemplarycatalyst composition having a metallocene concentration of 0.076mmole/gram of support material, and a MAO concentration of 3.84mmole/gram of support material, which, when used in an exemplaryembodiment of a polymerization process of the present invention,produced a polymer having a bulk density of 0.37 grams per cubiccentimeter. At 255 is illustrated an exemplary catalyst composition alsohaving a metallocene concentration of 0.076 mmole/gram of supportmaterial, and having a MAO concentration of 7.68 mmole/gram of supportmaterial, which, when used in an exemplary embodiment of apolymerization process of the present invention, produced a polymerhaving a bulk density of 0.47 grams per cubic centimeter. At 260 isillustrated an exemplary catalyst composition having a metalloceneconcentration of 0.038 mmole/gram of support material, and having a MAOconcentration of 7.68 mmole/gram of support material, which, when usedin an exemplary embodiment of a polymerization process of the presentinvention, produced a polymer having a bulk density of 0.48 grams percubic centimeter. At 265 is illustrated an exemplary catalystcomposition having a metallocene concentration of 0.038 mmole/gram ofsupport material, and having a MAO concentration of 3.84 mmole/gram ofsupport material, which, when used in an exemplary embodiment of apolymerization process of the present invention, produced a polymerhaving a bulk density of 0.37 grams per cubic centimeter. As theforegoing description of four reference points depicted in FIG. 2illustrates, exemplary catalyst compositions having, for example,comparatively lower MAO concentration produced polymer having arelatively lower bulk density when used in exemplary polymerizationprocesses of the present invention than did exemplary catalystcompositions having, for example, comparatively higher MAOconcentrations.

The relationship between an exemplary catalyst composition'sconcentration of MAO and metallocene, and the bulk density of thepolymer that may be produced from the use of such exemplary compositionin an exemplary polymerization process may be further evaluated byexamination of the bulk density regions (e.g., Region 202, 204, 206,208, 210, 212, 214, 216, 218, 220 and 222) depicted in FIG. 2 andsummarized in the table below.

TABLE 2 Bulk Density Range Region (gram/cubic centimeter) 202 less than0.33 204  0.33 to 0.346 206 0.346 to 0.362 208 0.362 to 0.378 210 0.378to 0.394 212 0.394 to 0.41 214  0.41 to 0.426 216 0.426 to 0.442 2180.442 to 0.458 220 0.458 to 0.474 222 above 0.474

For example, an exemplary catalyst composition (depicted at 250) havinga metallocene concentration of 0.076 mmole/gram of support material, andhaving a MAO concentration of 3.84 mmole/gram of support material,produced a polymer having a bulk density of 0.37 when used in anexemplary embodiment of a polymerization process of the presentinvention, and is therefore located in bulk density region 208 of FIG.2. Similarly, an exemplary catalyst composition (depicted at 260) havinga metallocene concentration of 0.038 mmole/gram of support material, andhaving a MAO concentration of 7.68 mmole/gram of support material,produced a polymer having a bulk density of 0.48 when used in anexemplary embodiment of a polymerization process of the presentinvention, and is therefore located in bulk density region 222 of FIG.2.

Method for Supporting

A support may also be present as part of the catalyst system of thepresent invention. Supports, methods of supporting, modifying, andactivating supports for single-site catalyst such as metallocenes arediscussed in, for example, 1 METALLOCENE-BASED POLYOLEFINS 173–218 (J.Scheirs & W. Kaminsky eds., John Wiley & Sons, Ltd. 2000). The terms“support” or “carrier”, as used herein, are used interchangeably andrefer to any support material, including inorganic or organic supportmaterials. In one exemplary embodiment, the support material may be aporous support material. Non-limiting examples of support materialsinclude inorganic oxides and inorganic chlorides, and in particular suchmaterials as talc, clay, silica, alumina, magnesia, zirconia, ironoxides, boria, calcium oxide, zinc oxide, barium oxide, thoria, aluminumphosphate gel, and polymers such as polyvinylchloride and substitutedpolystyrene, functionalized or crosslinked organic supports such aspolystyrene divinyl benzene polyolefins or polymeric compounds, andmixtures thereof, and graphite, in any of its various forms.

The support may be contacted with the other components of the catalystsystem in any number of ways. In one exemplary embodiment, the supportis contacted with the activator to form an association between theactivator and support, or a “bound activator”. In another exemplaryembodiment, the catalyst component may be contacted with the support toform a “bound catalyst component”. In yet another exemplary embodiment,the support may be contacted with the activator and catalyst componenttogether, or with each partially in any order. The components may becontacted by any suitable means as in a solution, slurry, or solid form,or some combination thereof. In certain exemplary embodiments, thecomponents may also be heated to a temperature in the range of from 25°C. to 250° C. while being contacted.

Desirable carriers are inorganic oxides that include Group 2, 3, 4, 5,13 and 14 oxides and chlorides. Support materials include silica,alumina, silica-alumina, magnesium chloride, graphite, and mixturesthereof in one exemplary embodiment. Other useful supports includemagnesia, titania, zirconia, montmorillonite (as described in EP 0 511665 B1), phyllosilicate, and the like. In certain exemplary embodiments,combinations of the support materials may be used, including, but notlimited to, combinations such as silica-chromium, silica-alumina,silica-titania, and the like. Additional support materials may includethose porous acrylic polymers described in EP 0 767 184 B1.

In one aspect of the support useful in the invention, the supportpossesses a surface area in the range of from 10 to 700 m²/gram, a porevolume in the range of from 0.1 to 4.0 cm³/gram and an average particlesize in the range of from 5 to 500 μm. In another exemplary embodiment,the carrier has a surface area in the range of from 50 to 500 m²/gram, apore volume of from 0.5 to 3.5 cm³/gram, and an average particle size offrom 10 to 200 μm. In yet another exemplary embodiment, the carrier hasa surface area in the range of from 100 to 400 m²/gram, a pore volumefrom 0.8 to 3.0 cm³/gram, and an average particle size of from 5 to 100μm. In still another exemplary embodiment, the carrier has a surfacearea in the range of from from 150 to 450 m²/gram, a pore volume in therange of from 1 to 2.5 cm³/gram and an average particle size in therange of from 10 to 50 μm. In another exemplary embodiment, the carrierhas a surface area in the range of from 250 to 400 m²/gram, a porevolume of from 1.25 to 2.0 cm³/gram, and an average particle size offrom 15 to 40 μm. In yet another exemplary embodiment, the carrier has asurface area in the range of from 300 to 350 m²/gram, a pore volume inthe range of from 1.5 to 1.75 cm³/gram, and an average particle size offrom 20 to 30 μm. Generally, the average pore size of the carrier rangesfrom 10 to 1000 Å. In one exemplary embodiment, the average pore size ofthe carrier is in the range of from 50 to 500 Å, while in yet anotherexemplary embodiment the average pore size ranges from 75 to 350 Å.

In one exemplary embodiment of the present invention, the support isgraphite. In one exemplary embodiment, the graphite is a powder; inanother exemplary embodiment, the graphite is flake graphite. In anotherexemplary embodiment, the graphite has a particle size of from 1 to 500microns. In still another exemplary embodiment, the graphite has aparticle size ranging from 1 to 400 microns, while in yet anotherexemplary embodiment, the graphite has a particle size in the range offrom 1 to 200 microns. In yet another exemplary embodiment, the graphitehas a particle size in the range of from 1 to 100 microns.

Dehydration or calcining of the support may also be carried out. In oneexemplary embodiment, the support is calcined prior to reaction with thefluorine or other support-modifying compound. In another exemplaryembodiment, the support is calcined and used without furthermodification, or calcined, then contacted with one or more activatorsand/or catalyst components. Suitable calcining temperatures range from100° C. to 1500° C. in one exemplary embodiment, and from 200° C. to1200° C. in another exemplary embodiment, and from 300° C. to 1000° C.in another exemplary embodiment, and from 350° C. to 900° C. in yetanother exemplary embodiment, and from 400° C. to 850° C. in yet a moreparticular exemplary embodiment, and from 800° C. to 900° C. in yet amore particular exemplary embodiment, and from 810° C. to 890° C. in yeta more particular exemplary embodiment, wherein a desirable rangeincludes any combination of any upper temperature limit with any lowertemperature limit. Calcining may take place in the absence of oxygen andmoisture by using, for example, an atmosphere of dry nitrogen.

The support, especially an inorganic support or graphite support, may bepretreated such as by a halogenation process or other suitable processthat, for example, associates a chemical species with the support eitherthrough chemical bonding, ionic interactions, or other physical orchemical interaction. In one exemplary embodiment, the support isfluorided. The fluorine compounds suitable for providing fluorine forthe support are desirably inorganic fluorine containing compounds. Suchinorganic fluorine containing compounds may be any compound containing afluorine atom as long as it does not contain a carbon atom. Particularlydesirable are inorganic fluorine containing compounds selected from thegroup consisting of NH₄BF₄, (NH₄)₂SiF₆, NH₄PF₆, NH₄F, (NH₄)₂TaF₇,NH₄NbF₄, (NH₄)₂GeF₆, (NH₄)₂SmF₆, (NH₄)₂TiF₆, (NH₄)₂ZrF₆, MoF₆,ReF₆,GaF₃, SO₂CIF, F₂, SiF₄, SF₆, ClF₃, ClF₅, BrF₅, IF₇, NF₃, HF, BF₃,NHF₂ and NH₄HF₂.

A desirable method of treating the support with the fluorine compound isto dry mix the two components by simply blending them at a concentrationof from 0.01 to 10.0 millimole F/g of support in one exemplaryembodiment, and in the range of from 0.05 to 6.0 millimole F/g ofsupport in another exemplary embodiment, and in the range of from 0.1 to3.0 millimole F/g of support in yet another exemplary embodiment. Thefluorine compound can be dry mixed with the support either before orafter the support is charged to the vessel for dehydration or calcining.Accordingly, the fluorine concentration present on the support is in therange of from 0.2 to 5 wt % in one exemplary embodiment, and from 0.6 to3.5 wt % of support in another exemplary embodiment.

Another method of treating the support with the fluorine compound is todissolve the fluorine in a solvent, such as water, and then contact thesupport with the fluorine containing solution (at the concentrationranges described herein). When water is used and silica is the support,it is desirable to use a quantity of water that is less than the totalpore volume of the support. Desirably, the support and, for example,fluorine compounds are contacted by any suitable means, such as by drymixing or slurry mixing at a temperature of from 100° C. to 1000° C. inone exemplary embodiment, and from 200° C. to 800° C. in anotherexemplary embodiment, and from 300° C. to 600° C. in yet anotherexemplary embodiment, the contacting in any case taking place forbetween two to eight hours.

It is within the scope of the present invention to co-contact (or“co-immobilize”) more than one catalyst component with a support.Non-limiting examples of co-immobilized catalyst components include twoor more of the same or different metallocene catalyst components, one ormore metallocene catalyst components co-immobilized with a Ziegler-Nattatype catalyst, one or more metallocene catalyst componentsco-immobilized with a chromium or “Phillips” type catalyst, one or moremetallocene catalyst components co-immobilized with a Group15-containing catalyst, and any of these combinations with one or moreactivators. More particularly, co-supported combinations includemetallocene A/metallocene A; metallocene A/metallocene B;metallocene/Ziegler Natta; metallocene/Group 15 containing catalyst;metallocene/chromium catalyst; metallocene/Ziegler Natta/Group 15containing catalyst; metallocene/chromium catalyst/Group 15 containingcatalyst, any of these with an activator, and combinations thereof.

In an exemplary embodiment, the supported catalyst(s) are treated bycombining them with the activators, and further combining them with upto 4.0 wt % (by weight of the catalyst composition) of an antistaticagent, such as an ethoxylated or methoxylated amine, an example of whichis Atmer AS-990 (available from Ciba of Tarrytown, N.Y.). In certainother exemplary embodiments of the present invention, the concentrationsof MAO and metallocene in the catalyst composition are optimized suchthat the antistatic agent is present in an amount less than 4.0 wt %,such as, for example, 2.0 wt %. In still other exemplary embodiments ofthe present invention, the concentrations of MAO and metallocene in thecatalyst composition are optimized such that the antistatic agent isabsent or substantially absent from the catalyst composition.

Polymerization Process

The polymerization process of the present invention may be carried outusing any suitable process, such as, for example, solution, slurry, highpressure, and gas phase. A particularly desirable method for producingpolyolefin polymers according to the present invention is a gas phasepolymerization process preferably utilizing a fluidized bed reactor.This type reactor, and means for operating the reactor, are well knownand completely described in, for example, U.S. Pat. Nos. 3,709,853;4,003,712; 4,011,382; 4,302,566; 4,543,399; 4,882,400; 5,352,749;5,541,270; EP-A-0 802 202 and Belgian Patent No. 839,380. These patentsdisclose gas phase polymerization processes wherein the polymerizationmedium is either mechanically agitated or fluidized by the continuousflow of the gaseous monomer and diluent.

In general, the polymerization process of the present invention may beeffected as a continuous gas phase process, such as a fluid bed process.A fluid bed reactor for use in the process of the present inventiontypically has a reaction zone and a so-called velocity reduction zone.The reaction zone includes a bed of growing polymer particles, formedpolymer particles and a minor amount of catalyst particles fluidized bythe continuous flow of the gaseous monomer and diluent to remove heat ofpolymerization through the reaction zone. Optionally, some of there-circulated gases may be cooled and compressed to form liquids thatincrease the heat removal capacity of the circulating gas stream whenreadmitted to the reaction zone. A suitable rate of gas flow may bereadily determined by simple experiment. Make up of gaseous monomer tothe circulating gas stream is at a rate equal to the rate at whichparticulate polymer product and monomer associated therewith iswithdrawn from the reactor, and the composition of the gas passingthrough the reactor is adjusted to maintain an essentially steady stategaseous composition within the reaction zone. The gas leaving thereaction zone is passed to the velocity reduction zone where entrainedparticles are removed. Finer entrained particles and dust may be removedin a cyclone and/or fine filter. The gas is passed through a heatexchanger wherein the heat of polymerization is removed, compressed in acompressor and then returned to the reaction zone.

More particularly, the reactor temperature of the fluid bed processherein ranges from 30° C. or 40° C. or 50° C. to 90° C. or 100° C. or110° C. or 120° C. or 150° C. In general, the reactor temperature isoperated at the highest temperature that is feasible taking into accountthe sintering temperature of the polymer product within the reactor.

The process of the present invention is suitable for the production ofhomopolymers of olefins, particularly ethylene, and/or copolymers,terpolymers, and the like, of olefins, particularly ethylene, and atleast one or more other olefin(s). Preferably the olefins are α-olefins.The olefins, for example, may contain from 2 to 16 carbon atoms in oneexemplary embodiment; and in another exemplary embodiment, ethylene anda comonomer comprising from 3 to 12 carbon atoms in another exemplaryembodiment; and ethylene and a comonomer comprising from 4 to 10 carbonatoms in yet another exemplary embodiment; and ethylene and a comonomercomprising from 4 to 8 carbon atoms in yet another exemplary embodiment.Polyethylenes are particularly preferred for preparation herein by theprocess of the present invention. Such polyethylenes are preferablyhomopolymers of ethylene and interpolymers of ethylene and at least oneα-olefin wherein the ethylene content is at least about 50% by weight ofthe total monomers involved. Exemplary olefins that may be used hereinare ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene,1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene and thelike. Also usable herein are polyenes such as 1,3-hexadiene,1,4-hexadiene, cyclopentadiene, dicyclopentadiene,4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene and5-vinyl-2-norbornene, and olefins formed in situ in the polymerizationmedium. When olefins are formed in situ in the polymerization medium,the formation of polyolefins containing long chain branching may occur.

In the production of polyethylene, comonomers may be present in thepolymerization reactor. When present, the comonomer may be present atany level with the ethylene monomer that will achieve the desired weightpercent incorporation of the comonomer into the finished resin. In oneexemplary embodiment of polyethylene production, the comonomer ispresent with ethylene in a mole ratio range of from 0.0001(comonomer:ethylene) to 50, and from 0.0001 to 5 in another exemplaryembodiment, and from 0.0005 to 1.0 in yet another exemplary embodiment,and from 0.001 to 0.5 in yet another exemplary embodiment. Expressed inabsolute terms, in making polyethylene, the amount of ethylene presentin the polymerization reactor may range to up to 1000 atmospherespressure in one exemplary embodiment, and up to 500 atmospheres pressurein another exemplary embodiment, and up to 200 atmospheres pressure inyet another exemplary embodiment, and up to 100 atmospheres in yetanother exemplary embodiment, and up to 50 atmospheres in yet anotherexemplary embodiment.

Hydrogen gas is often used in olefin polymerization to control the finalproperties of the polyolefin. Using the catalyst system of the presentinvention, it is known that increasing concentrations (partialpressures) of hydrogen increase the melt flow rate (MFR) and/or meltindex (MI) of the polyolefin generated. The MFR or MI can thus beinfluenced by the hydrogen concentration. The amount of hydrogen in thepolymerization can be expressed as a mole ratio relative to the totalpolymerizable monomer, for example, ethylene, or a blend of ethylene andhexane or propene. The amount of hydrogen used in the polymerizationprocesses of the present invention is an amount necessary to achieve thedesired MFR or MI of the final polyolefin resin. In one exemplaryembodiment, the mole ratio of hydrogen to total monomer (H₂:monomer) isin a range of from greater than 0.0001 in one exemplary embodiment, andfrom greater than 0.0005 in another exemplary embodiment, and fromgreater than 0.001 in yet another exemplary embodiment, and less than 10in yet another exemplary embodiment, and less than 5 in yet anotherexemplary embodiment, and less than 3 in yet another exemplaryembodiment, and less than 0.10 in yet another exemplary embodiment,wherein a desirable range may include any combination of any upper moleratio limit with any lower mole ratio limit described herein. Expressedanother way, the amount of hydrogen in the reactor at any time may rangeto up to 5000 ppm, and up to 4000 ppm in another exemplary embodiment,and up to 3000 ppm in yet another exemplary embodiment, and between 50ppm and 5000 ppm in yet another exemplary embodiment, and between 500ppm and 2000 ppm in another exemplary embodiment.

Further, it is common to use a staged reactor employing two or morereactors in series, wherein one reactor may produce, for example, a highmolecular weight component and another reactor may produce a lowmolecular weight component. In one exemplary embodiment of theinvention, the polyolefin is produced using a staged gas phase reactor.Such commercial polymerization systems are described in, for example, 2METALLOCENE-BASED POLYOLEFINS 366–378 (John Scheirs & W. Kaminsky, eds.John Wiley & Sons, Ltd. 2000); U.S. Pat. Nos. 5,665,818, 5,677,375, andEP-A-0 794 200.

The one or more reactor pressures in a gas phase process (either singlestage or two or more stages) may vary from 100 psig (690 kPa) to 500psig (3448 kPa), and in the range of from 200 psig (1379 kPa) to 400psig (2759 kPa) in another exemplary embodiment, and in the range offrom 250 psig (1724 kPa) to 350 psig (2414 kPa) in yet another exemplaryembodiment.

The gas phase reactor employing the catalyst system described herein iscapable of producing from 500 lbs of polymer per hour (227 Kg/hr) to200,000 lbs/hr (90,900 Kg/hr), and greater than 1000 lbs/hr (455 Kg/hr)in another exemplary embodiment, and greater than 10,000 lbs/hr (4,540Kg/hr) in yet another exemplary embodiment, and greater than 25,000lbs/hr (11,300 Kg/hr) in yet another exemplary embodiment, and greaterthan 35,000 lbs/hr (15,900 Kg/hr) in yet another exemplary embodiment,and greater than 50,000 lbs/hr (22,700 Kg/hr) in yet another exemplaryembodiment, and from 65,000 lbs/hr (29,000 Kg/hr) to 100,000 lbs/hr(45,500 Kg/hr) in yet another exemplary embodiment, and from 120,000lbs/hr (54,500 Kg/hr) to 150,000 lbs/hr (68,000 Kg/hr) in yet anotherexemplary embodiment.

In one exemplary embodiment of the invention, the polymerization processis a continuous gas phase process that includes the steps of:

-   (a) introducing a recycle stream (including ethylene and alpha    olefin monomers) into the reactor;-   (b) introducing the supported catalyst system;-   (c) withdrawing the recycle stream from the reactor;-   (d) cooling the recycle stream;-   (e) introducing into the reactor additional monomer(s) to replace    the monomer(s) polymerized;-   (f) reintroducing the recycle stream or a portion thereof into the    reactor; and-   (g) withdrawing a polymer product from the reactor.

A slurry polymerization process generally uses pressures in the range offrom 1 to 50 atmospheres and even greater, and temperatures in the rangeof 0° C. to 120° C. In a slurry polymerization, a suspension of solid,particulate polymer is formed in a liquid polymerization diluent mediumto which ethylene and comonomers and often hydrogen along with catalystare added. The suspension, including diluent, is intermittently orcontinuously removed from the reactor where the volatile components areseparated from the polymer and recycled, optionally after adistillation, to the reactor. The liquid diluent employed in thepolymerization medium is typically an alkane having from 3 to 7 carbonatoms, a branched alkane in one embodiment. The medium employed shouldbe liquid under the conditions of polymerization and relatively inert.When a propane medium is used, the process must be operated above thereaction diluent critical temperature and pressure. In one embodiment, ahexane or an isobutane medium is employed.

Another desirable polymerization technique of the invention is referredto as a particle form polymerization, or a slurry process where thetemperature is kept below the temperature at which the polymer goes intosolution. Other slurry processes include those employing a loop reactorand those utilizing a plurality of stirred reactors in series, parallel,or combinations thereof. Non-limiting examples of slurry processesinclude continuous loop or stirred tank processes. Also, other examplesof slurry processes are described in U.S. Pat. No. 4,613,484 and 2METALLOCENE-BASED POLYOLEFINS 322–332 (2000).

The slurry reactor employing the catalyst system described herein iscapable of producing greater than 2000 lbs of polymer per hour (907Kg/hr), and greater than 5000 lbs/hr (2268 Kg/hr) in another embodiment,and greater than 10,000 lbs/hr (4540 Kg/hr) in yet another embodiment.In another embodiment, the slurry reactor used in the process of theinvention produces greater than 15,000 lbs of polymer per hour (6804Kg/hr), and from 25,000 lbs/hr (11,340 Kg/hr) to 100,000 lbs/hr (45,500Kg/hr) in yet another embodiment.

In one exemplary embodiment of the process of the invention, the slurryor gas phase process is operated in the presence of a bulky ligandmetallocene-type catalyst system of the invention and in the absence of,or essentially free of, any scavengers, such as triethylaluminum,trimethylaluminum, tri-isobutylaluminum and tri-n-hexylaluminum anddiethyl aluminum chloride, dibutyl zinc and the like. By “essentiallyfree”, it is meant that these compounds are not deliberately added tothe reactor or any reactor components, and if present, are present toless than 1 ppm in the reactor.

As noted above, the polymerization process of the present invention maybe carried out by using a solution process. Nonlimiting examples ofsolution processes are described in, for example, U.S. Pat. Nos.4,271,060, 5,001,205, 5,236,998, and 5,589,555.

In another exemplary embodiment, one or all of the catalysts arecombined with up to 15 wt % of a metal-fatty acid compound, such as, forexample, an aluminum stearate, based upon the weight of the catalystsystem (or its components), such as disclosed in, for example, U.S. Pat.Nos. 6,300,436 and 5,283,278. Other suitable metals include other Group2 and Group 5–13 metals. In an alternate embodiment, a solution of themetal-fatty acid compound is fed into the reactor. In yet anotherexemplary embodiment, the metal-fatty acid compound is mixed with thecatalyst and fed into the reactor separately. These agents may be mixedwith the catalyst or may be fed into the reactor in a solution or aslurry with or without the catalyst system or its components.

The polymerization processes of the present invention use improvedmetallocene catalyst systems having optimized metals loading andactivator concentration. More particularly, the metallocene andactivator concentrations in the improved metallocene catalyst systems ofthe present invention are, in one exemplary embodiment, selected so asto maximize both the catalyst activity as well as the bulk density ofthe polymer product, while also maximizing the operability of thecatalyst (e.g., minimizing the Fouling Index). Generally, themetallocene catalyst is present in the improved metallocene catalystsystems of the present invention in an amount in the range of from 0.01to 1.0 mmole metallocene per gram of support material. In certainpreferred embodiments, the metallocene catalyst is present in theimproved metallocene catalyst systems of the present invention in anamount in the range of from 0.04 to 0.1 mmole metallocene per gram ofsupport material. In certain more preferred embodiments, the metallocenecatalyst is present in the improved metallocene catalyst systems of thepresent invention in an amount in the range of from 0.05 to 0.08 mmolemetallocene per gram of support material. In certain most preferredembodiments, the metallocene catalyst is present in the improvedmetallocene catalyst systems of the present invention in an amount inthe range of from 0.06 to 0.07 mmole metallocene per gram of supportmaterial. Generally, an increase in the amount of metallocene present inthe catalyst compositions of the present invention, with all othervariables being held constant, tends to increase the activitydemonstrated by the catalyst composition when used in the polymerizationprocesses of the present invention, and slightly decrease the bulkdensity of the polymer product that is produced. The amount ofmetallocene present in the catalyst compositions of the presentinvention, with all other variables being held constant, generally doesnot affect the reactor Fouling Index that is observed.

For example, the polymerization processes of the present invention,using catalyst systems having a metallocene catalyst concentration in anamount in the range of from 0.01 to 1.0 mmole metallocene/gram supportmaterial, generally have a reactor Fouling Index in the range of from 0to 2; a catalyst activity of at least 2,500 gram polymer per gramcatalyst per hour; and produce a polymer product having a bulk densityof at least 0.30 gram per cubic centimeter. In certain preferredembodiments wherein the metallocene catalyst concentration is in therange of from 0.04 to 0.1 mmole metallocene/gram of support material,the Fouling Index remains in the range of from 0 to 2; and the activityis increased to at least 2,800 gram polymer per gram catalyst per hour.In certain more preferred embodiments wherein the metallocene catalystconcentration is in the range of from 0.05 to 0.08 mmolemetallocene/gram of support material, the activity is increased to atleast 4,000 gram polymer per gram catalyst per hour. In certain mostpreferred embodiments wherein the metallocene catalyst concentration isin the range of from 0.06 to 0.07 mmole metallocene/gram of supportmaterial, the activity is increased to at least 4,200 gram polymer pergram catalyst per hour.

The polymerization process may be optimized by modulating themetallocene concentration and the MAO concentration in the catalystsystem so as to maximize both the catalyst activity as well as the bulkdensity of the polymer product, while minimizing the reactor FoulingIndex. For example, in one embodiment of the present invention, thecatalyst system has a metallocene concentration in the range of from0.05 to 0.08 mmole metallocene/gram of support material, and a MAOconcentration in the range of from 5.5 to 6.5 mmole MAO/gram of supportmaterial, thereby reducing the Fouling Index to 0 while increasing thecatalyst activity to at least 5,600 gram polymer per gram catalyst perhour, and increasing the bulk density of the polymer product to at least0.45 gram per cubic centimeter. In another exemplary embodiment of thepresent invention, the catalyst system has a metallocene concentrationin the range of from 0.06 to 0.07 mmole metallocene/gram of supportmaterial, and a MAO concentration in the range of from 6 to 6.5 mmoleMAO/gram of support material, thereby reducing the Fouling Index to 0while increasing the catalyst activity to at least 6,000 gram polymerper gram catalyst per hour, and increasing the bulk density of thepolymer product to at least 0.46 gram per cubic centimeter.

In an exemplary embodiment, the present invention provides a process ofpolymerizing olefins wherein: (a) ethylene and at least one comonomerselected from the group consisting of C4 to C8 alpha olefins; and (b) asupported catalyst system including a metallocene catalyst compoundactivated by methylaluminoxane, and a support material, themethylaluminoxane being present in the range of from 3 to 9 mmolemethylaluminoxane per gram of support material, the metallocene beingpresent in the range of from 0.01 to 1.0 mmole metallocene per gram ofsupport material; are contacted in a reactor; wherein the catalyst hasan activity of at least 2,500 grams polyethylene per gram of catalystcompound per hour; and the process produces a polymer having a bulkdensity of at least 0.30 gram/cubic centimeter.

Polymer Product of the Invention

The polyolefins of the present invention may be blended with additivesto form compositions that can then be used in articles of manufacture.Those additives include antioxidants, nucleating agents, acidscavengers, plasticizers, stabilizers, anticorrosion agents, blowingagents, other ultraviolet light absorbers such as chain-breakingantioxidants, etc., quenchers, antistatic agents, slip agents, pigments,dyes and fillers and cure agents such as peroxide. These and othercommon additives in the polyolefin industry may be present in polyolefincompositions from 0.01 to 50 wt % in one exemplary embodiment, and from0.1 to 20 wt % in another exemplary embodiment, and from 1 to 5 wt % inyet another exemplary embodiment, wherein a desirable range may includeany combination of any upper wt % limit with any lower wt % limit.

In particular, antioxidants and stabilizers such as organic phosphites,hindered amines, and phenolic antioxidants may be present in thepolyolefin compositions of the invention from 0.001 to 5 wt % in oneexemplary embodiment, from 0.01 to 0.8 wt % in another exemplaryembodiment, and from 0.02 to 0.5 wt % in yet another exemplaryembodiment. Non-limiting examples of organic phosphites that aresuitable are tris(2,4-di-tert-butylphenyl)phosphite (IRGAFOS 168) anddi(2,4-di-tert-butylphenyl)pentaerithritol diphosphite (ULTRANOX 626).Non-limiting examples of hindered amines includepoly[2-N,N′-di(2,2,6,6-tetramethyl-4-piperidinyl)-hexanediamine-4-(1-amino-1,1,3,3-tetramethylbutane)symtriazine](CHIMASORB 944); bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate (TINUVIN770). Non-limiting examples of phenolic antioxidants includepentaerythrityl tetrakis(3,5-di-tert-butly-4-hydroxyphenyl) propionate(IRGANOX 1010); and1,3,5-Tri(3,5-di-tert-butyl-4-hydroxybenzyl-isocyanurate (IRGANOX 3114).

Fillers may be present from 0.1 to 50 wt % in one exemplary embodiment,and from 0.1 to 25 wt % of the composition in another exemplaryembodiment, and from 0.2 to 10 wt % in yet another exemplary embodiment.Desirable fillers include, but are not limited to, titanium dioxide,silicon carbide, silica (and other oxides of silica, precipitated ornot), antimony oxide, lead carbonate, zinc white, lithopone, zircon,corundum, spinel, apatite, Barytes powder, barium sulfate, magnesiter,carbon black, dolomite, calcium carbonate, talc and hydrotalcitecompounds of the ions Mg, Ca, or Zn with Al, Cr or Fe and CO₃ and/orHPO₄, hydrated or not; quartz powder, hydrochloric magnesium carbonate,glass fibers, clays, alumina, and other metal oxides and carbonates,metal hydroxides, chrome, phosphorous and brominated flame retardants,antimony trioxide, silica, silicone, and blends thereof. These fillersmay particularly include any other fillers and porous fillers andsupports known in the art.

Fatty acid salts may also be present in the polyolefin compositions ofthe present invention. Such salts may be present from 0.001 to 2 wt % ofthe composition in one exemplary embodiment, and from 0.01 to 1 wt % inanother exemplary embodiment. Examples of fatty acid metal salts includelauric acid, stearic acid, succinic acid, stearyl lactic acid, lacticacid, phthalic acid, benzoic acid, hydroxystearic acid, ricinoleic acid,naphthenic acid, oleic acid, palmitic acid, and erucic acid, suitablemetals including Li, Na, Mg, Ca, Sr, Ba, Zn, Cd, Al, Sn, Pb and soforth. Desirable fatty acid salts are selected from magnesium stearate,calcium stearate, sodium stearate, zinc stearate, calcium oleate, zincoleate, and magnesium oleate.

With respect to the physical process of producing the blend ofpolyolefin and one or more additives, sufficient mixing should takeplace to assure that a uniform blend will be produced prior toconversion into a finished product. The polyolefin suitable for use inthe present invention can be in any physical form when used to blendwith the one or more additives. In one exemplary embodiment, reactorgranules (defined as the granules of polymer that are isolated from thepolymerization reactor) are used to blend with the additives. Thereactor granules have an average diameter of from 10 μm to 5 mm, andfrom 50 μm to 10 mm in another exemplary embodiment. Alternately, thepolyolefin is in the form of pellets, such as, for example, pelletshaving an average diameter of from 1 mm to 6 mm that are formed frommelt extrusion of the reactor granules.

One method of blending the additives with the polyolefin is to contactthe components in a tumbler or other physical blending means, thepolyolefin being in the form of reactor granules. This can then befollowed, if desired, by melt blending in an extruder. Another method ofblending the components is to melt blend the polyolefin pellets with theadditives directly in an extruder, Brabender or any other melt blendingmeans.

The resultant polyolefin and polyolefin compositions of the presentinvention may be further processed by any suitable means such as bycalendering, casting, coating, compounding, extrusion, foaming; allforms of molding including compression molding, injection molding, blowmolding, rotational molding, and transfer molding; film blowing orcasting and all methods of film formation to achieve, for example,uniaxial or biaxial orientation; thermoforming, as well as bylamination, pultrusion, protrusion, draw reduction, spinbonding, meltspinning, melt blowing, and other forms of fiber and nonwoven fabricformation, and combinations thereof. These and other forms of suitableprocessing techniques are described in, for example, PLASTICS PROCESSING(Radian Corporation, Noyes Data Corp. 1986).

In the case of injection molding of various articles, simple solid stateblends of the pellets serve equally as well as pelletized melt stateblends of raw polymer granules, of granules with pellets, or of pelletsof the two components, since the forming process includes a remeltingand mixing of the raw material. In the process of compression molding ofmedical devices, however, little mixing of the melt components occurs,and a pelletized melt blend would be preferred over simple solid stateblends of the constituent pellets and/or granules. Those skilled in theart will be able to determine the appropriate procedure for blending ofthe polymers to balance the need for intimate mixing of the componentingredients with the desire for process economy.

The polymers of the present invention, in one exemplary embodiment, havea melt index (MI) or (I₂) as measured by ASTM-D-1238-E (190/2.16) in therange from 0.01 dg/min to 1000 dg/min, more preferably from about 0.01dg/min to about 100 dg/min, even more preferably from about 0.1 dg/minto about 50 dg/min, and most preferably from about 0.1 dg/min to about10 dg/min, and even more preferably from 0.1 dg/min to 5 dg/min.

The polymers of the present invention, in one exemplary embodiment, havea melt index ratio (I₂₁/I₂) (I₂₁ is measured by ASTM-D-1238-F,[190/21.6]) of from 5 to 300, more preferably from about 10 to less than250, and from 15 to 200 in yet another exemplary embodiment, and from 20to 180 in yet another exemplary embodiment, and from 15 to 30 in yetanother exemplary embodiment, and from 10 to 40 in yet another exemplaryembodiment, and from 5 to 50 in yet another exemplary embodiment,wherein a desirable range may include any combination of any upper limitwith any lower limit.

The polymers of the present invention have a bulk density measured inaccordance with ASTM-D-1238 that, in one exemplary embodiment, isgreater than at least 0.30 grams per cubic centimeter. In anotherexemplary embodiment, the bulk density of the polymers is in the rangeof 0.30 to 0.50 grams per cubic centimeter.

Common rheological properties, processing methods and end useapplications of metallocene based polyolefins are discussed in, forexample, 2 METALLOCENE-BASED POLYOLEFINS 400–554 (John Scheirs & W.Kaminsky, eds. John Wiley & Sons, Ltd. 2000). The polyolefiniccompositions of the present invention are suitable for such articles asfilms, fibers and nonwoven fabrics, extruded articles and molded.Examples of films include blown or cast films formed by coextrusion orby lamination useful as shrink film, cling film, stretch film, sealingfilms, oriented films, snack packaging, heavy duty bags, grocery sacks,baked and frozen food packaging, medical packaging, industrial liners,membranes, etc. in food-contact and non-food contact applications,agricultural films and sheets. Examples of fibers include melt spinning,solution spinning and melt blown fiber operations for use in woven ornon-woven form to make filters, diaper fabrics, hygiene products,medical garments, geotextiles, etc. Examples of extruded articlesinclude tubing, medical tubing, wire and cable coatings, pipe,geomembranes, and pond liners. Examples of molded articles includesingle and multi-layered constructions in the form of bottles, tanks,large hollow articles, rigid food containers and toys, etc.

Other desirable articles that can be made from and/or incorporate thepolyolefins of the present invention include automotive components,sporting equipment, outdoor furniture (e.g., garden furniture) andplayground equipment, boat and water craft components, and other sucharticles. More particularly, automotive components include such asbumpers, grills, trim parts, dashboards and instrument panels, exteriordoor and hood components, spoiler, wind screen, hub caps, mirrorhousing, body panel, protective side molding, and other interior andexternal components associated with automobiles, trucks, boats, andother vehicles.

Further useful articles and goods may be formed economically orincorporate the polyolefins produced by the practice of our inventionincluding: crates, containers, packaging material, labware, office floormats, instrumentation sample holders and sample windows; liquid storagecontainers for medical uses such as bags, pouches, and bottles forstorage and IV infusion of blood or solutions; wrapping or containingfood preserved by irradiation, other medical devices including infusionkits, catheters, and respiratory therapy, as well as packaging materialsfor medical devices and food which may be irradiated by gamma orultraviolet radiation including trays, as well as stored liquid,particularly water, milk, or juice, containers including unit servingsand bulk storage containers.

EXAMPLES

In order to provide a better understanding of the present invention,including representative advantages thereof, the following examples ofsome exemplary embodiments are offered. In no way should such examplesbe read to limit the scope of the invention.

The catalyst composition and the polymer produced in the Examples weretested and synthesized as follows: A 2 liter autoclave reactor under anitrogen purge was charged with 0.16 mmoles triethylaluminum (TEAL),followed by 60 cubic centimeters (cc) of 1-hexene comonomer and 800 ccof isobutane diluent. The contents of the reactor were heated to 80° C.,after which 100 mg of each of the supported polymerization catalystsprepared in Examples 1 to 27 (the preparation of which is describedfurther below) were each separately polymerized as follows: eachpolymerization catalyst was introduced concurrently with ethylene intothe reactor to make up a total reactor pressure of 325 psig (2,240 kPa).The reactor temperature was maintained at 85° C. and the polymerizationwas allowed to proceed for 40 minutes. After 40 minutes the reactor wascooled, ethylene was vented off, and the polymer dried and weighed toobtain the polymer yield. Tables 1 through 5 below providepolymerization results, along with the fouling characteristics observed,and other physical properties of the polymers.

Density was measured in accordance with ASTM-D-1238. Catalyst activitywas measured in grams of polyethylene (PE) per gram of polymerizationcatalyst in one hour (gPE/gCat·h).

Example Set A

Preparation of Supported Metallocene Catalyst

Example 1

In a 125 ml glass vial equipped with a stirring bar and under anaerobicconditions was added 20 ml of toluene, and 6.64 ml of a 30 wt %methylaluminoxane (MAO) solution (1.85 gram MAO, 6.40 mmol/gram silica)(available from Albemarle Corporation of Baton Rouge, La.). Whilestirring, 0.082 grams (0.038 mmol/gram silica) ofbis(1,3-methyl-n-butylcyclopentadienyl) zirconium difluoride metallocenedissolved in 2 ml of toluene were added to the glass vial. The mixturewas stirred at room temperature (25° C.) for 15 minutes, after which 5grams of ES-757 silica (dehydrated at 600° C.) (available from IneosSilicas of Warrington, UK), was added to the solution. The ES-757 silicaexhibits the following physical properties:

Physical Properties ES-757 Surface Area (M²/gram) 316 Pore Volume(cm³/gram) 1.59 10th % μ 9 50th % μ 25 90th % μ 45The mixture was then stirred for 15 minutes after which the catalyst wasdried at 75° C. until the solid was free flowing.

Examples 2–8

The catalysts in Examples 2–8 were prepared similarly to the catalyst inExample 1 with the exception that the amount of MAO and metallocene(MCN) were adjusted in the manner shown in Table 3.

TABLE 3 mmole MAO mmole MCN Activity Fouling Example g SiO₂ g SiO₂(gPE/gCat · h) Index 1 6.40 0.038 4164 0 2 6.40 0.050 5532 0 3 6.400.063 6540 0 4 6.40 0.076 6811 0 5 3.84 0.063 4300 0 6 5.12 0.063 5133 07 6.40 0.063 6560 0 8 7.68 0.063 7580 1Slurry Polymerizations Using the Catalysts in Examples 1–8

Polymerization was conducted as described above, and the activity andFouling Index results for each catalyst sample are shown in Table 3.Results indicate that as the MCN amount was increased with a constantMAO loading, the activity of the catalyst increased and the foulingstayed the same. The data also show that as the MAO loading increased,at a constant MCN loading, the catalyst activity increased, but thefouling tendency increased.

Example Set B

Preparation of Supported Metallocene Catalyst

The catalysts in Examples 9–17 were prepared similarly to the catalystin Example 1 with the exception that the amount of MAO and metallocene(MCN) were adjusted as shown in Table 4.

TABLE 4 mmole MAO mmole MCN Activity Fouling Example g SiO₂ g SiO₂(gPE/gCat · h) Index 9 7.68 0.038 5173 1 10 7.68 0.050 5870 1 11 7.680.063 7580 1 12 7.68 0.076 8500 2 13 3.84 0.038 2614 0 14 5.12 0.0384082 0 15 6.40 0.038 4164 0 16 7.68 0.038 5173 1 17 8.96 0.038 5125 2Slurry Polymerizations Using the Catalysts in Examples 9–17

Polymerization was conducted as described above and the results areshown in table 4. Results again indicate that the activity increasedwith increasing metals loading on the catalyst.

Example Set C

Preparation of Supported Metallocene Catalyst

The catalysts in Examples 18–27 were prepared similarly to the catalystin Example 1, with the exception that the amount of MAO and metallocene(MCN) was adjusted as shown in tables 5 and 6.

TABLE 5 Resin Bulk mmole MAO mmole MCN Density Example g SiO₂ g SiO₂(g/cc) 18 6.40 0.038 0.48 19 6.40 0.050 0.48 20 6.40 0.063 0.45 21 6.400.076 0.45

TABLE 6 Resin Bulk mmole MAO mmole MCN Density Example g SiO₂ g SiO₂(g/cc) 22 3.84 0.063 0.35 23 5.12 0.063 0.41 24 6.40 0.063 0.45 25 6.400.038 0.47 26 7.68 0.038 0.48 27 8.96 0.038 0.48

The results illustrate, inter alia, that the resin bulk density stayedconstant or marginally declined as MCN loading was increased. However,as the MAO loading was increased, as in Examples 23–27, the resin bulkdensity increased.

While the present invention has been described and illustrated byreference to particular exemplary embodiments, those of ordinary skillin the art will appreciate that the invention lends itself to variationsnot necessarily illustrated herein. For example, it is contemplated thatmetallocene catalyst compounds of the invention may be introduced into areactor in a mineral oil slurry, or introduced to the process of theinvention to boost activity or productivity, or simply to improve theoperability of the process. For this reason, then, reference should bemade solely to the appended claims for purposes of determining the truescope of the present invention.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties, reaction conditions, and so forth, used in thespecification and claims are to be understood as approximations based onthe desired properties sought to be obtained by the present invention,and the error of measurement, etc., and should at least be construed inlight of the number of reported significant digits and by applyingordinary rounding techniques. Notwithstanding that the numerical rangesand values setting forth the broad scope of the invention areapproximations, the numerical values set forth are reported as preciselyas possible.

1. A process of polymerizing olefins comprising contacting, in areactor: (a) ethylene and at least one comonomer selected from the groupconsisting of C₄ to C₈ alpha olefins; and (b) a supported catalystsystem comprising a metallocene catalyst compound activated bymethylaluminoxane, and a support material, the methylaluminoxane beingpresent on the range of from 3 to 7.7 mmole methylaluminoxane per gramof support material, the metallocene being present in the range of from0.04 to 0.1 mmole metallocene per gram of support material; wherein theprocess produces a polyethylene copolymer having a bulk density of atleast 0.30 gram/cubic centimeter; and wherein the support material issilica having an average particle size ranging from 10 to 40 μm, andwherein the metallocene catalyst compound is a substitutedbis-cyclopentadienyl zirconocene catalyst compound comprising at leastone fluoride or fluorine containing leaving group.
 2. The process ofclaim 1 wherein the polymerization process is a gas phase process. 3.The process of claim 1 wherein the polymerization process is a slurryprocess.
 4. The process of claim 1 wherein an antistatic agent ispresent in the catalyst composition in an amount less than 4% by weightof the catalyst composition.
 5. The process of claim 4 wherein theantistatic agent is present in the catalyst composition in an amount inthe range of from 0% to 2% by weight of the catalyst composition.
 6. Theprocess of claim 1 wherein the metallocene catalyst compound is selectedfrom the group consisting of: bis(1,3-methyl-n-butylcyclopentadienyl)zirconium difluoride; bis(n-propylcyclopentadienyl) zirconiumdifluoride; (tetramethyl cyclopentadienyl) (n-propyl cyclopentadienyl)zirconium difluoride; and (pentamethyl cyclopentadienyl) (n-propylcyclopentadienyl) zirconium difluoride.
 7. The process of claim 1wherein the methylaluminoxame is present in an amount in the range offrom 4 to 7.7 mmole methylaluminoxane per gram of support material. 8.The process of claim 7 wherein the methylaluminoxane is present in anamount in the range of from 5 to 6.5 mmole methylaluminoxane per gram ofsupport material.
 9. The process of claim 8 wherein themethylaluminoxane is present in an amount in the range of from 6 to 6.5mmole methylaluminoxane per gram of support material.
 10. The process ofclaim 9 wherein the metallocene catalyst compound is present in anamount in the range of from 0.06 to 0.07 mmole metallocene per gram ofsupport material.
 11. The process of claim 1 wherein an antistatic agentis absent or substantially absent from the catalyst composition.
 12. Theprocess of claim 11 wherein the support material has a surface area inthe range of from 150 to 450 m²/gram.
 13. The process of claim 11wherein the support material has a pore volume in the range of from 1 to2.5 cm³/gram.
 14. The process of claim 1 wherein the support materialhas a surface area in the range of from 150 to 450 m²/gram.
 15. Theprocess of claim 14 wherein the support material has a surface area inthe range of from 250 to 400 m²/gram.
 16. The process of claim 15wherein the support material has a surface area in the range of from 300to 350 m²/gram.
 17. The process of claim 1 wherein the polymer producedhas a bulk density of at least 0.4 grams per cubic centimeter.
 18. Theprocess of claim 17 wherein the polymer produced has a bulk density ofat least 0.48 grams per cubic centimeter.
 19. The process of claim 1wherein the support material has a pore volume in the range of from 1 to2.5 cm³/gram.
 20. The process of claim 19 wherein the support materialhas a pore volume in the range of from 1.25 to 2.0 cm³/gram.
 21. Theprocess of claim 20 wherein the support material has a pore volume inthe range of from 1.5 to 1.75 cm³/gram.
 22. The process of claim 21wherein the support material has an average particle size of from 20 to30 μm.